By the use of isotope imaging devices including the position scintillation camera and the Donner Laboratory Mark II whole-body scanner, combined with the short-lived positron-emitteing isotopes of iron and fluoride, it is possible to visualize the distribution of erythropoietic marrow within the skeleton and the relative flow of blood to various parts of the skeleton. The imaging devices have been interfaced to a digital computing system. Techniques are being devised to obtain quantitative data on the spatial and temporal movement of these physiological tracers through the body making appropriate corrections fo tissue absorption and contributions to measured activity from adjacent tissues. Studies have demonstrated a remarkable similarity in distribution o bone blood flow and distribution of erythropoietic marrow in normal man and afimals. In addition to the measurement of overall bone blood flow calcualted from the extraction of F18 from the general circulation local marrow isotope turnover is being determined by tracer washout methods after direct intrameduallary injection in dogs. Improved quantitative data on the relation of bone blood flow and hematopoiesis are being sought in disorders of bone and of blood including Paget's disease of bone and myelofibrosis. These quantitative studies are aimed at determining the role of bone pathophysiology in blood dyscrasias.